Accident Overview
On November 30, 2017, at 1540 Pacific standard time, a Robinson Helicopter Company R22, registration N47WH, sustained substantial damage when it impacted the ground during an instructional flight near Truckee, California. The two pilots on board were seriously injured. The flight was conducted under Title 14 Code of Federal Regulations Part 91.
Flight Details
The flight instructor reported that the helicopter had been purchased by the pilot/owner and was delivered the morning of the accident. Earlier that day, the instructor flew the helicopter to comply with recent flight experience requirements. The accident flight occurred in the afternoon with the owner aboard. The purpose was to evaluate the helicopter's flight characteristics with two full-size adults to determine its suitability as a training helicopter. If performance was satisfactory, the instructor and owner planned to practice procedures and maneuvers required for a biennial flight review.
The instructor stated that they practiced several maneuvers, including normal takeoffs, pattern work, normal and steep approaches, landings, hover work, governor-off maneuvers, hovering autorotations, and low rpm recovery in a hover. After these maneuvers, they decided to perform straight-in autorotations followed by 180° autorotations.
During a 180° autorotation setup, while on downwind, the instructor noted that the helicopter was not flying smoothly and suspected an unbalanced main rotor with a "little hop." This vibration had not been observed on earlier flights. The maneuver continued. After passing the intended landing point, the instructor initiated the autorotation from about 700 feet above ground level (agl) at 80 knots indicated airspeed. Approximately one-third through the 180° turn, he felt a need for a desirable speed, so he moved the cyclic forward and adjusted the collective accordingly. When about two-thirds through the turn, he found he lacked cyclic and collective control and anticipated a crash. He continued to call out "rpm, airspeed, and outside" while making control inputs to the unresponsive aircraft. No flare or engine rpm recovery was attempted at the end.
Witness Account
A witness at the airport observed the helicopter practicing pattern work east of runway 29. The witness saw the helicopter turn onto its base leg at a normal attitude, then enter a rapid descent toward the runway. The helicopter flared about 30 yards from the runway, struck the ground tail rotor first, followed by the main body. The main rotor blades severed the tail boom, and the helicopter came to rest on its side.
Postaccident Examination
Examination of the airframe revealed flight control continuity. The tail cone separated after contact by a main rotor blade. The throttle linkage was intact and in the closed position. The mixture was set to full rich, and carburetor heat was off. Both V-belts were out of their sheave grooves, with one belt fractured across the vees. The fuel tanks were half-full, verified visually and by the fuel gauges.
The engine sustained minimal impact damage. The crankshaft rotated smoothly by hand using the cooling fan. Thumb compression was present in all cylinders, and spark was produced at the lower ignition leads during crankshaft rotation.
Weather and Weight
The automated weather observation station at Truckee-Tahoe Airport (TRK) reported at 1545: wind from 290° at 5 knots, temperature 50°F, dewpoint 23°F, and altimeter setting 30.17 inches of mercury. The airport elevation is 5,904.3 feet mean sea level (msl), with a calculated density altitude of 6,469 feet.
The maximum gross takeoff weight for the R22 Beta II is 1,370 lbs. The estimated gross weight at the time of the accident was about 1,356 lbs.